Dispersion relation for spherical electromagnetic resonances in the atmosphere

An analytic model is developed to describe atmospheric lightning flash fiel ds by use of a normal mode expansion with frequency dependent ionospheric h eights. The calculated magnetic field spectra are compared to modeling with the residue series formula the normal mode expansion with constant ionosph eric heights, and measured magnetic field spectra. The proposed new model e xhibits the best agreement with the measured magnetic field spectra. The re sults are summarized in a complex dispersion relation k = omega/cS(2) for e lectrodynamic extremely low frequency wave propagation in the atmosphere an d make possible global ionospheric monitoring. (C) 2000 Elsevier Science B. V. All rights reserved.